After a century of work on high blood pressure, do we understand it? In part, yes. Most of us agree—as a prejudiced observer I would rather say, admit— that essential hypertension mainly derives from the brain. In their Lead Article, Julian Paton and Mohan Raizada concentrate on the rat. Why does an animal model of hypertension created by selective inbreeding seem to have especially involved the brain's blood supply? The arteries of the brainstem in spontaneous hypertensive rats (SHRs; developed by Aoki and Okamoto) are much smaller than those in the Wistar-Kyoto rats from which SHRs were derived. The arterial endothelium in SHRs appears to be unduly sticky. It encourages dense leukocyte adhesion that may restrict blood flow and compromise oxygen delivery to important nuclei. These include the nuclei of the solitary tracts, which (in humans) lie in the floor of the 4th ventricle at the level of the obex. There, they receive afferent nerve impulses from the arterial baroreceptors and connect with inhibitory caudal medullary nuclei. The latter have connections with rostral ventrolateral medullary nuclei whose activity increases when inhibition is withdrawn. A comparable complicated reciprocal system presumably underlies the human “baroreflex” relating arterial pressure inversely to heart rate...